Production and Quality

1.What are the thermal characteristics of large-aperture infrared lenses at different temperatures? As the temperature drops, the thermal deformation of the optical lens increases. This is because the lens barrel,O-ring and other mechanical parts squeeze the lens, which increases the thermal stress of the lens. The surface shape of the lens changes uniformly in a low temperature environment. This is because the lens is radially squeezed by the mechanical structure. When the temperature rises to 60°C, the surface shape of the lens changes irregularly, Larger thermal deformation also occurs in a relatively normal temperature environment, but less thermal deformation than in low temperature environment, this is because there will be a gap between mechanical components and lens in high temperature environment, which reduces the thermal stress of the lens, and the thermal deformation of the lens is correspondingly reduced; compared with high temperature and low temperature environment The image quality will decrease in normal temperature environment, and the imaging performance in low temperature environment is worse than that in high temperature environment. 2.What effect does stray radiation have on large-aperture infrared lenses? Generally, the first lens of a large-aperture infrared lens has a larger aperture than a conventional infrared lens, and the luminous flux entering the infrared system is more, causing external stray light to easily enter the opto-mechanical system. When there is a strong radiation source outside the field of view, the observed target signal energy is very weak, causing the non-target imaging energy outside the field of view to exceed the target imaging energy, so that the low-contrast target image or image details are overwhelmed, causing stray light on the image surface of the detector system.

The curve of the infrared radiation received by the detector varies with the parameters, and the change trend is clear: at low altitude, the infrared radiation received by the detector decreases linearly with the increase of the detection height; it shows a Gaussian distribution with the change of the azimuth angle; The increase of visibility increases exponentially. When the visibility is less than a certain distance, with the increase of visibility, the increasing trend of infrared radiation gradually strengthens, and after reaching a certain distance, its increasing trend gradually slows down; with the increase of relative humidity, it is logarithmic When the relative humidity is low, the change is relatively slow, when the relative humidity is close to saturation, the rate of decline accelerates sharply; it decreases linearly with the increase of carbon dioxide content. Under the same conditions, the radiation attenuation in the long-wave band is smaller than that in the medium-wave band, and the attenuation rate of radiation in summer is significantly smaller than that in winter. (The Gaussian distribution curve is bell-shaped, low at both ends and high in the middle, and symmetrical to the left and right because the curve is bell-shaped.) （Quote—Li Fei. Analysis of Atmospheric Transmission Impact on Mid-wave and Long-wave Infrared Radiation [J]. Infrared Technology, 2019, 41(4): 315.）

1. What are the advantages and disadvantages of 2D drawings and 3D models? 2D Drawings: Advantages: It can completely express parts of all necessary information for manufacturing and processing, including dimensions, technical specifications, tolerance. The drawings can be converted into various formats, and printed (or output) drawings can be moved, shared and read in various environments. Disadvantages: The drawing is complex and people requires certain professional knowledge to fully understand the information presented. 3D Models: Advantages: The model is intuitive and clear, with well-defined relationships between parts. Even non-professionals can have a general understanding of the designed product through the 3D model. In addition, 3D models are easy to design and modify, which can greatly save design time and improve work efficiency. Moreover, 3D models are also convenient for sharing resource information. Disadvantages: Specific software is needed to view detailed information. 3D models cannot intuitively express dimension data, surface roughness, and technical specification. In short, customers can use 2D drawings to understand the product's approximate dimensional information, structure, shape, and so on. If you want to have a deeper understanding of the product, you can use 3D models, which can provide a more intuitive and three-dimensional display of the product, and offer a more comprehensive design understanding and evaluation. (Take the GCZ92513KD as an example) 3D Model    2D Drawing 2. Does the dimensional deviation of the parts need to be consistent? No need to keep consistent. Dimensional deviation refers to the extent to which the dimension and shape of a part deviate from the design requirements due to various factors during the machining process. Each dimension of a part can have different dimensional deviations. Designers need to set appropriate dimensional deviations based on specific design requirements and actual manufacturing processes. 3. What are the factors that affect part dimensional deviation? Factors affecting the dimensional deviation of parts include human factors, equipment, process and materials. Analyzing the main factors affecting parts machining errors is crucial for improving machining quality and reducing errors.

In winter, not only low temperature is a factor that affects infrared cameras, but also the sealing performance of each component is a significant challenge. Low temperature will impact the performance of electronic components, such as decreased battery life, electro-optical system malfunctions, etc. Low temperature, rain or snow will also cause internal fogging and condensation, affecting the lens and the inside of the body. So you need to pay attention to the following points:1. Cold weather protectionBefore use, make sure the battery is fully charged to maintain normal voltage. Facilitate battery preheating to enhance chemical activity internally, ensuring the normal functioning of all components. Avoid voltage dips and prevent damage to fragile plastic components in low-temperature environments. Prevent safety hazards such as freezing of components.2. Snow and Rain ProtectionRain, snow and icing are also serious problems. Be sure to promptly clean up any ice or snow covering the camera's surface. If liquid is observed on the camera's surface, wipe it clean to prevent potential freezing during use.After the ice and snow melt, moisture in the gaps will more easily enter the interior of the camera. When clearing, we can use various tools, but try to avoid using substances with chemical reagents, as they may corrode internal circuit boards. If fogging occurs inside the lens, you can accelerate the dissipation of water vapor in the lens by turning on and preheating.3. Static electricity and precautionsWinter clothing tends to be thick, contributing to a higher likelihood of static electricity buildup. And static electricity is the most easily ignored topic in winter. Given that static electricity can lead to poor contact or even short circuits, it is essential to power off the camera when operating. Additionally, it is advisable to touch a metal object before operating to avoid the risks associated with static electricity.4. Dryness and moisture-proof precautionsIn addition to moisture protection, it is crucial to prevent excessive dryness during winter. Overly dry environments will also produce certain hazards, especially to lens components. In severe cases, it can cause the coating to crack and peel off, and easily lead to cracks in the rubber of the camera.

In the process of performing reconnaissance and strike missions, UAVs need to carry various electro-optical payloads, such as infrared thermal imaging cameras, laser rangefinders, etc. During flight, the UAV’s attitude movement and the windage torque will cause the boresight pointing to be unstable. These external factors will seriously affect the imaging quality of the electro-optical equipment carried by the UAV, resulting in blurred images and reduced clarity. In aviation electro-optical imaging equipment, inertial sensors are usually used to measure carrier disturbance information, and control algorithms are used to compensate for the disturbance to achieve stable control of the boresight in the inertial space. However, the control of the electro-optical stabilization platform is a complex, coupled, and nonlinear problem, involving many factors such as the field of mechanical design, mathematical modeling methods, servo control systems, and sensor measurement technologies.The main function of the airborne electro-optical platform is to isolate external disturbances, such as the aircraft's own shaking, wind drag disturbances during flight, and internal disturbances of the electro-optical platform. This ultimately enhances the pointing precision of the electro-optical platform's boresight and improves imaging quality. Operating within a complex airborne environment, the platform is affected by complex multi-source factors during flight, making the compensation of external disturbances crucial for achieving high-precision pointing of boresight.Passive vibration reduction and isolation stability: Use vibration isolators installed on the outer frame or inner frame of the electro-optical platform to isolate external disturbances.Active compensation stabilization is used to obtain image stability, including overall stabilization, electronic stabilization, and mirror stabilization. The overall stability is to use the inertial components installed inside the electro-optical platform to monitor the position and attitude of the platform in real time, and provide timely feedback of the monitored data, and then adjust the parameters and motor drive circuits to maintain the stability of the boresight.

1. Security SurveillanceWidely employed in video security surveillance for sensitive areas such as shopping malls, communities, banks, warehouses, etc., especially for night security.2. Personal consumptionCommonly used in outdoor activities like adventures and field scientific expeditions. Some manufacturers have developed mobile phones with plug-in thermal imaging devices for daily temperature measurement and personal entertainment.3. Driver AssistanceInstalled in vehicles, boats and other transportation to provide drivers auxiliary observation information of the road conditions ahead by displaying infrared thermal images, thereby avoiding potential road traffic safety hazards such as haze, smoke and heavy rain.4. Fire and policeUtilized in search and rescue operations for various accidents, including earthquakes, fires, traffic accidents, aircraft accidents, and beach scenarios. Infrared detection enables police officers to conduct searches, observations, or tracking during night or concealed conditions.5. Industrial monitoringApplicable to control processes in almost all industrial manufacturing, especially the monitoring and temperature control of production processes under smoke, effectively ensuring product quality and production processes.6. Power monitoringUsed for observing the operating status of mechanical and electrical equipment. It can express equipment faults in the form of temperature images and find the source of danger before the equipment is damaged by high temperatures and conduct maintenance in advance, thereby improving equipment production capacity, reducing maintenance costs, and shortening downtime for maintenance.7. Medical quarantineBy observing the temperature differences of affected bodies or pathological tissues, and distinguishing sick bodies among groups for inspection, infrared thermal imaging cameras play a vital role in promptly detecting sick bodies and avoiding the spread of the epidemic.

An infrared optical window is a selectively transparent component designed based on its material to allow specific wavelengths of light to pass through. These windows are carefully designed to maintain optical clarity, withstand environmental conditions, and minimize any distortion or alteration of the light passing through them. They are primarily used to protect precision optical elements, facilitate measurements, and enable observation or imaging in various applications.

EO/IR stands for "Electro-Optical/Infrared," a comprehensive technology that integrates Electro-Optical (EO) and Infrared (IR) sensing. Both technologies are used for the detection and acquisition of light and thermal radiation in different wavelength bands, enabling surveillance, reconnaissance, navigation, and other applications. Specifically:Electro-Optical (EO) sensing technology encompasses visible light and optical sensors, such as cameras and telescopes, used to capture images and videos within the visible light spectrum.Infrared (IR) sensing technology involves infrared sensors that detect the thermal radiation emitted or reflected by objects. IR technology is useful in situations where there is low light or where a heat source needs to be detected.The combined use of these two technologies enables a more comprehensive approach to target detection, identification, and tracking, providing 360° awareness in day&night. Common applications of EO/IR systems include airborne homeland security, military, patrols, surveillance, reconnaissance, search and rescue missions.

Thermal sensitivity (NETD) stands for Noise Equivalent Temperature Difference, which is a critical parameter for evaluating Medium-Wave Infrared (MWIR) and Long-Wave Infrared (LWIR) thermal imaging cameras. It is a value that represents the signal-to-noise ratio of the temperature difference, which is equivalent to the instantaneous noise of the imaging camera. Therefore, it approximately represents the minimum temperature difference that the thermal imaging camera can resolve, which is directly related to the clarity of its measurement. When selecting sensors with the same pixel configuration and under a fixed thermometric scale, using instruments with different thermal sensitivities to take pictures, the results are as follows:  Under different thermal sensitivities, the pictures presented are very different. The smaller the value of sensitivity, the better the thermal sensitivity and the clearer the picture.  Measurement of NETD(1) Two-point MethodThe two-point method is a common way to measure the NETD of an infrared imaging camera. It is based on two assumptions: 1. The surface of the target is uniform without local heat sources. 2. The noise between the pixels of the imaging camera is independent.The specific steps are as follows: 1. In a completely dark environment, select two pixel points with moderate spacing as the target point. 2. Measure the output signal of the thermal imaging camera and calculate the signal difference between the two pixels.3. Calculate the corresponding NETD according to the temperature characteristics of the thermal imaging camera.(2) Averaging MethodThe averaging method is a simple and commonly used method for measuring the NETD of thermal imaging cameras. It is based on the statistical properties of the imaging camera output signal for higher measurement accuracy.The specific steps are as follows: 1. Select an appropriately sized pixel area under stable environmental conditions. 2. Measure the average and standard deviation of the output signals of all pixels in the area.  3. Calculate the NETD based on the temperature characteristics and standard deviation of the thermal imaging camera.(3) Spectrum Analysis MethodSpectral analysis is a method of measuring the NETD of an infrared imaging camera based on the signal spectrum, which is suitable for thermal imaging cameras with obvious noise frequency characteristics.The specific steps are as follows: 1. The signal output by the imaging camera is subjected to Fourier transform to obtain the spectrum of the signal. 2. Analyze the noise components in the spectrum and calculate the NETD. Factors affecting NETD:(1) Corrected Temperature Measurement Range. Depending on the selected temperature measurement range and object temperature, the noise readings will be different. However, as long as there is significant thermal contrast in the image and the temperature of the target area is much higher than the background temperature, it will not affect the measurement accuracy too much.(2) Detector temperature. If the imaging camera is placed at a higher temperature, the system noise will increase, the extent of which depends on the internal stability of the infrared thermal imaging camera. (3) The F-number of the camera lens. A lower F-number means a larger aperture, which allows more infrared radiation to enter the camera. Generally, a larger aperture (lower F-number) receives more infrared radiation, which helps to improve the signal-to-noise ratio of the imaging. In theory, the lower the F-number, the lower the noise values and the better the image quality.

The infrared sight consists of objective lens, shell, eyepiece, battery, connector, etc., as shown in the diagram 1. Diagram 1 Infrared sight composition1. Objective lens; 2. Shell; 3.Battery;4. Eyepiece; 5. Connector The basic working principles of infrared sight is as shown in the figure below. Figure  Infrared sight’s working principle figure The infrared sight is mounted to the firearm Picatinny rail via the connector; the infrared radiation from the target is focused by the objective lens assembly onto the sensitive element of the infrared uncooled focal plane detector. After thermal-electric conversion, a processable electrical signal is generated. The electronic circuit board performs pre-treatment of the electrical signal and converts it into a digital image signal. Then the digital image signal undergoes non-uniformity correction, blind pixel replacing, image enhancement, brightness and contrast adjustment and overlay of menu, interface and firing table information before being output to the eyepiece, so as to assist the shooter in achieving accurate shooting.

Infrared sights works at infrared bands, whose characteristics of imaging have a obvious advantage over white light sights, having a significant meaning in the modern battlefield.Firstly, all the objects emit infrared radiation, which infrared sights can transmit into electrical signal, then process and form digital image displayed on the eyepiece, enabling it to operate around the clock; Secondly, infrared wavelength is longer than visible light wavelength, and infrared has a much stronger ability to penetrate fog than visible light, so as to effectively identify the target through the smoke on the battlefield;Last, the imaging displayed by infrared sights is the temperature difference between target and environment, which is not affected by the disguise of visible light, enabling it to identify the target better.       

1. The composition and working principle of laser rangefinder: ·The laser rangefinder consists of an optical system, a laser, a drive circuit, a receiving circuit, a signal processing circuit, a system power circuit and an external data interface circuit, as shown in the figure below: The laser rangefinder uses the pulse distance measurement method. Its working principle is to calculate the distance using the time required for the laser pulse to be emitted and returned. The specific steps are as follows: ·The signal processing circuit receives the ranging command sent by the upper computer through the external data interface circuit, and then sends the control signal to the drive circuit. ·After receiving the control signal, the drive circuit injects an electrical pulse signal into the laser. The laser pulse laser output from the laser is sent to the detected target by the optical transmitting system, ·And simultaneously the main wave collected by the receiving circuit is sent to the signal processing circuit after truing. ·Reflected back by the target, the laser signal is converged to the receiving circuit through the receiving optical system, and then sent to the signal processing circuit after amplification and truing. ·The signal processor receives the main wave and echo to realize data sampling, counting and calculation. ·After completing data processing, the signal processing circuit uploads the distance information to the upper computer, so as to complete a distance measurement. The calculation formula for the pulse ranging method is: ·LRF G1535 L6 as an example, as shown in the figure below: after connecting the upper computer with it, the pulse laser is output from bit 1 to the target through signal processing and conduction. Then the laser signal reflected back by the target is transmitted by the receiving optical system through the bit 2. And after data conversion, it is transmitted back to the upper computer, finally completing the distance measurement.  2. The application of laser rangefinder: · The laser rangefinder is light in weight, small in size, simple in operation, fast and accurate, with the error only one fifth to several hundredths of other optical rangefinders. Therefore, it is widely used in terrain measurement, battlefield measurement, ranging of tanks, aircraft, ships and artillery to targets, measuring the altitude of clouds, aircraft, missiles, and artificial satellites, etc. It is an important technical equipment to improve the accuracy of tanks, aircraft, ships and artillery, and is also widely used in industrial measurement and control, mines, ports and other fields. 

The stray lights will exist in every optical-mechanical system, which is impossible to completely eliminate, but can be reduced through certain methods. The methods of suppressing stray lights are mainly three aspects: optical design, mechanical structure and surface finishing. ·  In terms of optical design, stray lights can be suppressed by the design of optical lenses, characteristics of mirror plane, the degree of lens finish, optical filter and the design of      diaphragm. ·  In terms of mechanical structure, there are two ways: one is designing a shading structure mainly including lens hoods, blocking rings, shading baffles and so on; the other is designing an extinction screw thread in the inner wall of modules such as lens barrels. ·  In terms of surface finishing, it can reduce the Bidirectional Scattering Distribution Function(BSDF) on the surface to suppress the stray lights by changing the roughness, blackening, painting the matting agent, coating the lens surface with anti-reflection film and so on.       

With the development of computer hardware and software technology and its application in the design of optoelectronic systems, many representative design and simulation tools and software sprung up. These include: ZEMAX, CODE V, OSLO, LENSVIEW, ASAP, TRACEPRO, LIGHTTOOL, TFCALC, OPTISYS_DESIGN, ASLD, Multisim, COMSOL Multiphysics and so on. Here is a brief introduction and analysis of ZEMAX and CODE V, which are commonly used for infrared lens design.1. ZEMAXZEMAX, the optical design software, is a suite of operating Sequential and Non-Sequential calculators. It can be used for the design of optical components, for the modelling of reflections, refractions and diffraction, and for combining of optimization and tolerance analysis. It can integrate the design concepts, optimization, analysis, tolerances and reporting of real optical systems into a comprehensive set of optical design simulation software.The main features of ZEMAX:· Multi-functional analysis graphics, parameter selection via dialogue window, user-friendly analysis and definition;      · Analysis graphics can be saved as graph files, such as x.bmp, *.jpg, etc., but also as text files *.txt;      · Merit function parameter input via table column type, preset merit function parameter dialogue window type; and provides a variety of optimization methods;      · Tolerance parameter input via table column type and preset tolerance parameter via dialogue window type;      · A variety of graphical report output, the results can be saved as graph files and text files.2. CODE VCODE V is used to model, analyze, optimize, and provide fabrication support for the development of optical systems with diverse applications. It provides a powerful, yet easy-to-use toolkit of optical techniques and calculations.In addition to such basic capabilities as lens modeling and spot diagrams, CODE V has a vast array of technical, graphical, and ease-of-use features. The following list of "key features" is just a small subset of what is available capabilities.· Optimization (including Global Synthesis)· Ease of use (GUI interface and commands)· Extensive built-in libraries of optical system models (patents, etc.), components, and optical glass· Extensive graphics (pictures, data plots, shaded displays), including 3D visualizations and diffraction-based image simulations· Database/modeling Features· Tolerancing (including extremely fast and accurate wavefront differential tolerancing)· Interferogram interface (supports computer-aided closed-loop alignment)· Non-sequential surface modeling for unusual systems· Powerful command language (with Macro-PLUS programming)· Fast 2D Image Simulation with an input bitmap file (including diffraction)· The most accurate, efficient beam propagation analysis available· CODE V is the most comprehensive "tool box" for optical modeling, design and analysis available today.CODE V is the most comprehensive optical design and analysis program in the world. It has led the way with a long series of innovations. These include:· Zoom/multi-configuration optimization and analysis· Environmental/thermal analysis· Fast wavefront differential tolerancing for MTF, RMS wavefront error, fiber coupling efficiency, polarization dependent loss, and Zernike wavefront coefficient performance metrics· User-defined constraints in optimization· Interferometric interface and optical alignment· Non-sequential surface modeling· Vector diffraction calculations including polarization· Global Synthesis®, the first practical global optimization method for optical design· And many moreCODE V also includes a powerful Macro-PLUS programming language, a flexible, user-friendly graphical user interface (GUI), and features for analysis of illumination in optical systems. As with all features of CODE V, these capabilities offer outstanding depth, generality, and applicability to real-world problems.